Hello all:
I plan to do some long distance cruising when I retire in 6 years. Any opinions on aluminum vs SS for a radar arch on a Cape Dory 33? I plan a few solar panels, windvane. Radar is already on the mast.

Stainless steel will be stronger -- you say "a few" solar panels but don't say what size or how many, but if it's more than just 1x40W panel (for example) then stainless will be the way to go. You could use solid aluminium (rod not tubing) but I think that would defeat the weight advantage that aluminium would otherwise have.

One of the problems with alumium is the welded joints are very much weaker than the parent material which is why it is best to have bolted connections. Not a problem with stainless which can be welded without the loss in strength. Also looks nicer